Clutch linings of this type are used particularly for friction clutches in motor vehicles, in which they are riveted to a metallic carrier plate or clutch disk, in order to enable, in conjunction with a counterelement, a force transmission between an engine and a transmission in the coupled state and, with the clutch open, to decouple said force transmission.
In this case, the clutch linings have to satisfy stringent requirements because they should fulfill many requirements which cannot readily be achieved in the same way. In particular, the clutch lining should have a high burst rotational speed, so as not to be destroyed by centrifugal forces, should have a high coefficient of friction by means of which a high torque can be transferred, and should at the same time have low wear and be resistant to deforming distortion due to heat and/or force influences. Nevertheless, the clutch linings should be capable of being produced in as uncomplicated a way as possible and therefore economically.
To increase the bursting strength, that is to say the strength of the clutch lining in the circumferential direction, it is already known to deposit a binder-impregnated yarn material in a plurality of flat plies in a wavy manner in the circumferential direction, the turns of this strand material having radially inner and radially outer reversal regions which lie on concentric circles (DE 44 20 291 B4). In particular, the reversal regions of the turns may in each case be distributed to a plurality of concentric circles having different diameters, the radii of the circles differing from one another sufficiently to avoid thickenings at the margins of the clutch lining or lining body which may otherwise lead to pressure damage to the yarn material. The fraction of yarn material in the overall composition of the lining body material can consequently be increased.
Winding mostly takes place with the aid of a winding machine, one ply being wound in a circumferential direction per revolution, as defined.
Such yarn material wound in the form of an annular disk, as shown, for example, in FIG. 1, is also designated as a winding or preform. The imaginary circle with an outside diameter of the friction part in the form of an annular disk is itself also designated as the outside diameter of the winding, and the same applies to the inside diameter. The radially inner and radially outer reversal regions of the turns on the yarn material wound in the form of an annular disk are tangent to the inside and the outside diameter of the winding.
The winding ratio indicates how often the yarn in each case is tangent to an imaginary circle with an outside diameter of the friction part in the form of an annular disk or of the dimensionally similar reinforcing part, or, in other words, how often the yarn is tangent to the outside diameter during one revolution of an annular part. A winding ratio of 1:2.6 states that the yarn touches the outside diameter 2.6 times during one revolution on account of the turns. A winding ratio of 1:4 is in this case lower than a winding ratio of 1:5 and is not to be interpreted in the sense of a division.
When a spiral is wound, winding may be carried out from the inside diameter to the outside diameter, or vice versa. In order to wind such a spiral, the winding machine requires a plurality of revolutions from tangent to the inside diameter as far as tangent to the outside diameter, or vice versa. This required number of revolutions corresponds to the number of turns of the spiral.